A survey was carried out in 2003 in 49 dairy herds to determine the overall and pathogen-specific prevalence of intramammary infection (IMI) in Dutch dairy herds, and to compare the distribution with four studies performed from 1973 to 1985 in The Netherlands. Herds were randomly selected stratified over the 12 Dutch provinces, had at least 40 lactating cows and participated in the Dutch milk recording system. Quarter milk samples were collected from all 408 cows with a somatic cell count (SCC) ⩾250 000 cells/ml and 145 heifers with SCC ⩾150 000 cells/ml at the last milk test before the farm visit. Additionally, samples were collected from 519 (approximately 25%) of the remaining low-SCC cows and heifers with a SCC at the last milk test before the farm visit of <250 000 and <150 000 cells/ml, respectively. Bacterial growth occurred in 37·3% of milk samples of high-SCC cows and in 21·1% of low-SCC cows. Coagulase-negative staphylococci (CNS) were the most frequently isolated group of bacteria (10·8% of quarters) and were found in all herds. Prevalence of Staphylococcus aureus IMI was lower in 2003 than in 1973, respectively 1·8% and 6·2% of quarters. Prevalence of Streptococcus uberis and Str. dysgalactiae IMI was almost the same in the five samplings during the 30-year period, at 1·1–1·7 and 0·9–1·5%, respectively. Str. agalactiae was not found in this study. Prevalence of CNS IMI was higher in lactating heifers, while prevalence of Str. uberis, Str. dysgalactiae and penicillin-resistant Staph. aureus IMI was higher in older cows. Because distribution of pathogens changes over time, herd-level samples for bacteriological culturing must be taken regularly to monitor udder health. Additionally, national mastitis prevalence studies give important information through monitoring the national udder health status.

Staphylococcus haemolyticus is a pathogen frequently isolated from dairy cows and small ruminants. However, it always appears in only a few animals and not as a major pathogen. Recently, in a dairy goat herd of approximately 250 milking animals, 25·6% (46/180 goats) had milk cultures with atypical highly mucoid colonies accompanied by elevated somatic cell counts. The isolates were identified as Staph. haemolyticus. The present study describes the steps used in an attempt to identify the bacterium and to compare it with other coagulase-negative staphylococci (CNS) including Staph. haemolyticus. Species identification performed with the API STAPH-IDENT 32 kit showed >99·4% identity confirmed by 16S rDNA sequencing tests. Microscopically the atypical Staph. haemolyticus strains showed unique cuboidal tetrad clusters reminiscent of those of the genus Sarcina. The outbreak caused by an atypical CNS underlines the need for accurate biochemical and genetic methods for ultimate identification of CNS to the species level.

A total of 24 lactating Holstein cows averaging 620 (se=29) kg of body weight were allotted at week 17 of lactation to eight groups of three cows blocked for similar days in milk to determine the effects of feeding two sources of the plant lignan precursor secoisolariciresinol diglucoside, whole flaxseed and flaxseed meal, on concentrations of the mammalian lignans (enterodiol and enterolactone) in milk. Feed intake, digestion, milk production and milk composition were also determined to compare the use of whole flaxseed and flaxseed meal for milk production. Cows within each block were assigned to one of the three isonitrogenous and isoenergetic total mixed diets: no flaxseed product; 10% flaxseed meal; or 10% whole flaxseed in the dry matter. The experiment was carried out from week 17 to week 21 of lactation and diets were fed at ad-libitum intake. The mammalian lignan, enterodiol, was not detected in the milk of cows. Cows fed whole flaxseed and flaxseed meal had greater concentrations of enterolactone in milk than those fed the control diet. Feed intake, milk production and milk composition were also similar for all diets, indicating that both flaxseed meal and whole flaxseed are suitable feed ingredients for milk production of cows in mid lactation. The results provide new information on the conversion of plant secoisolariciresinol diglucoside from two flaxseed products into mammalian lignans in dairy cows.

In present study, three strains of lactic acid bacteria (LAB) viz. Lactobacillus casei, Lactobacillus acidophilus and Lactococcus lactis and milk fermented with these strains have been studied for antioxidant and cholesterol assimilation activities in-vitro and in-vivo, in addition to the effect on total lactobacilli, lactococci and coliform counts into the gut of mice fed with diets supplemented by fermented milk. All three selected strains exhibited potent 2,2-diphenyl-1-picrylhydrazyl, malonaldialdehyde and hydrogen peroxide radical scavenging abilities as well as inhibition of linoleic acid peroxidation activity. These activities were highest in Lb. casei as followed by Lb. acidophilus and Lc. lactis. In addition, these bacterial cultures also exhibited good in-vitro cholesterol assimilation potential. Oral administration to mice of milk fermented with selected LAB strains, slightly decreased blood cholesterol, increased colonization of total lactobacilli and lactococci, and decreased coliforms in the intestinal tissues as well as faecal samples. These results indicate that, selected LAB strains have good antioxidant, hypocholesterolemic and coliform removal activities. It may suggest that, a novel functional food can be obtained by supplementation of selected LAB in milk, which may have various health beneficial properties such as antioxidant and hypocholesterolemic activities.

Enterococci represent an important part of bacterial microbiota in different types of artisanal cheeses, made from either raw or pasteurized milk. Polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) of ribosomal DNA is currently one of the most frequently used fingerprinting method to study diversity and dynamics of microbial communities and also a tool for microbial identification. Among several primer pairs for DGGE analysis published so far, six primer pairs amplifying different variable regions of 16S rDNA were selected and applied in our DGGE analysis of 12 species belonging to genus Enterococcus and eight other bacterial species often found in cheeses (seven lactobacilli and one Lactoccocus lactis). When DGGE procedures were optimized, the same set of primers was used for DGGE analysis of five cheese samples. Our study demonstrates that the use of different primer pairs generate significant differences in DGGE analysis of enterococcal population, consequently, appropriate primers regarding the purpose of analysis can be selected. For differentiation and identification of pure enterococcal isolates, primer pair P1V1/P2V1 showed the most promising results since all 12 enterococcal isolates gave distinctive DGGE fingerprints, but with multiple bands patterns; therefore, these primers do not seem to be appropriate for identification of enterococcal species in mixed cultures. Use of primer pairs HDA1/HDA2 and V3f/V3r amplifying V3 region showed better potential for detection and identification of enterococci in mixed communities, but since some bacterial species showed the same fingerprint, for clear identification combination of DGGE and some other method (e.g. species specific PCR) or combined DGGE analysis using two primer pairs generating distinctive results should be used.

An experiment was conducted with 12 lactating dairy ewes and 12 goats with the objective to determine whether, under the same dietary treatments, the differences in their fatty acid (FA) profile with emphasis on cis-9 trans-11 CLA milk fat content, are reflected in the transcript levels of genes involved in FA and cis-9, trans-11 CLA biosynthesis. The animals were fed with two diets (A, B) in different days of milk (DIM) due to the different milk yield, body weight etc, in order to have the same food intake and to avoid dietary effects. Diet A was fed to the animals on a group basis as it is traditionally used in practice, while diet B was chosen to avoid individual feed intake variation which is usually observed in group feeding. The results showed that there are significantly lower mRNA levels of acetyl-CoA carboxylase (ACC) in sheep mammary gland compared with those of goats, independently from the diet fed. The same trend was observed with the mRNA level of FA synthase (FAS), but the results were significant only for diet A. The mRNA level of lipoprotein lipase (LPL) in the mammary gland did not differ between sheep and goats fed with diet A. In addition, the concentration of cis-9 trans-11 CLA content was significantly higher in sheep milk fat compared with those of goats. This is in accordance with the significant higher levels on mRNA of stearoyl-CoA desaturase (SCD) which were observed in their mammary adipocytes of sheep compared with those of goats, independently of the fed diet (A or B). In conclusion, these findings demonstrate that the differences between sheep and goats, concerning cis-9, trans-11 CLA and FA milk fat content, under the same dietary treatments could be explained in part by the differences in mRNA of SCD and lipogenic genes in their mammary gland.

A study was carried out to analyse the production and composition of milk from Malagueña goats of different genotypes for the content of αs1-casein. Twenty goats were used, half of them with a high (HG) and half with a low (LG) genetic capability for αs1-casein synthesis. Among the ten HG goats, seven had BB and three had AB genotypes, whereas there were seven EF and three FF genotypes among the LG goats. The goats were fed a diet differing in crude protein content, 136 and 177 g/kg dry matter for diet 1 (D1) and diet 2 (D2), respectively. For each genotype group, a trial was conducted, with each of the two diets in a two-period balanced change-over design, in which the milk production and composition were analysed. The genotype was found to determine milk composition, with that produced by the HG goats being higher in total solids, protein, αs1-casein, αs2-casein and fat. Analysis of milk production values and, especially, those of the yields of the different components, revealed an interaction between the factors. HG goats that consumed D1 were more productive than LG goats, but this ceased to be so when the D1 diet was replaced by D2. However, LG goats, although less productive than HG ones when the D1 diet was consumed, showed increased productive capacity when D1 was replaced by D2. The main difference for the fatty acid profile of the dairy fat is that the milk fat produced by the HG goats contained higher levels of short and medium-chain fatty acids. From these results, it is concluded that, in terms of favouring production, the advantage of replacing animals with a low capacity for αs1-casein synthesis with those of a high capacity seems to depend on the protein level in the diet. Similarly, the advantage of changing to a diet of higher protein content depended on the animal's genotype.

There have been increases in the number of organic dairy farms in the UK in recent years. However, there is little information on the impact of organic regulations on cow welfare. As part of a larger study, we aimed to investigate differences between organic and non-organic farms in management practices and winter housing quality. Forty organic and 40 non-organic farms throughout the UK were visited. Organic and non-organic farms were paired for housing type, and as far as possible for herd size, genetic merit and location. A detailed questionnaire covering key aspects of dairy management was carried out with each farmer. On a subset of twenty pairs, an assessment of the quality of the winter housing for both lactating and dry cows was undertaken, covering the parlour, bedding, loafing and feeding areas. Management practices and building conditions varied greatly within farm types and there was considerable overlap between organic and non-organic farms. Milk yield, level and composition of concentrate feed, management of heifers and calving, and use of ‘alternative treatments’ to prevent and treat mastitis differed between organic and non-organic farms. In all other respects there were no differences between farm types. Building dimensions per cow did not differ, even though organic recommendations advise greater space per cow than recommended for non-organic farms. The similarity between organic and non-organic farms in most respects indicates that cow housing and health, based on both the described management regimes and the farmers' perceptions of disease incidence, on organic dairy farms is neither compromised by the regulations, nor considerably better than on non-organic farms.

Coagulase-negative staphylococci (CNS) have emerged as bovine mastitis pathogens in many countries. CNS mastitis is generally mild but can persist in the udder for long periods. Pathogenesis of CNS intramammary infection is not well understood. In the present study, adhesion, invasion and intracellular replication of twenty-two CNS strains isolated from bovine mastitis and the effect of bovine lactoferrin (bLf) on the internalization were studied in vitro in a bovine mammary epithelial (BME) cell model. The CNS strains were of Staphylococcus chromogenes, Staph. simulans, Staph. epidermidis, Staph. haemolyticus and Staph. cohnii urealyticus; two strains of Staph. aureus were used as controls. Seven of the CNS strains originated from persistent and five from transient mastitis infections. The in-vitro susceptibility of the strains to bLf was also investigated. All CNS species examined had an adhesive ability equal to that of Staph. aureus, but internalization varied among staphylococcal strains. The antagonistic effect of bLf on the adhesion and invasion of CNS strains was weak, but bLf significantly decreased intracellular replication and replication rates of CNS. No correlation between the in-vitro susceptibility of the strain to bLf or internalization among clinical signs of mastitis was established. No difference between the persistent and transient CNS strains in adhesion, invasion or replication rate was recorded. This in-vitro BME cell model can be used to study the virulence potential of mastitis pathogens, although the severity and persistence of eventual infections shall be further investigated in vivo. The role of bLf in intramammary infection caused by CNS may be limited.

Goats are often kept on small farms where they suckle kids and are hand milked for human consumption. Our first objective was to investigate whether vasopressin secretion increases together with oxytocin during hand milking and suckling in seven goats 6–8 weeks after parturition. Four goats suckled and three were hand milked on the first day and the treatments were reversed on the next day. Blood samples were taken via a semi-permanent catheter. Plasma concentrations of vasopressin and oxytocin increased during suckling, but not during hand milking. Plasma cortisol concentration was elevated for 10 min after both treatments. These results initiated a second series in which the objectives were to measure vasopressin and oxytocin concentrations during hand milking in a larger number of goats and to investigate whether the rise in cortisol concentration was due to the experimental conditions or to milking, by adding a no-milking treatment. Nine goats in lactation weeks 4–10 were studied. Heart rate and arterial blood pressure were registered in eight of the goats. Oxytocin concentration did not change during hand milking and the vasopressin concentration was below the detection limit. Heart rate and blood pressure were elevated during milking and for about 10 min thereafter. Cortisol concentration increased after milking, as above. None of the variables changed in the no-milking treatment. This suggests that the rise in cortisol concentration was due to milk excretion and was not a stress reaction. In conclusion, suckling increased plasma concentrations of vasopressin and oxytocin, but hand milking did not. In a mixed system, presence of the kids may be necessary to stimulate release of the peptides and thereby contraction of the myoepithelial cells. However, milk stored in the udder cisterns can be obtained by hand milking without presence of oxytocin or vasopressin.

Organic dairy farming is an expanding segment of the dairy sector where cow management differs from the conventional model in many respects. Thus, a comparative evaluation of disease and welfare status in organically and conventionally managed dairy cows is required. Assessment of milk yield, udder health and reproductive performance (RP) was done in 20 organically and 20 conventionally managed Swedish dairy herds. In accordance with earlier findings we confirmed lower milk yield in organic cows. Udder health and RP were chosen as indicators of animal health in view of their clinical relevance and the availability of appropriate data bases providing good background knowledge for further animal health assessment. No obvious differences were found in the investigations of somatic cell count (SCC) profiles or time to veterinary-treated cases of mastitis between organically and conventional managed cows. Pregnancy success at first insemination, an appropriate measurement of RP with biological interpretation and background, did not reveal any difference between management types, whereas the hazard rate-ratio (HR) of having a calving-interval was significantly lower (HR=0·71) in organically managed cows. The calving-interval is an important financial determinator in dairy production, but it is not considered an optimal indicator of biologic relevance as it partially reflects farmer decisions. In conclusion, the organically managed cows in this study did not differ from conventionally managed cows in udder health or RP, with the exception of calving interval.

To test a system with milk flow-controlled pulsation, milk flow was recorded in 29 Holstein cows during machine milking. The three different treatments were routine milking (including a pre-stimulation of 50–70 s), milking with a minimum of teat preparation and milking with milk flow-controlled b-phase, i.e. with a gradually elongated b-phase of the pulsation cycle with increasing milk flow rate and shortening again during decreasing milk flow. For data evaluation the herd was divided into three groups based on the peak flow rate at routine milking (group 1: <3·2 kg/min; group 2: 3·2–4·5 kg/min; group 3: >4·5 kg/min). Compared with routine milking, milking with milk flow-controlled b-phase caused a significant elevation of the peak flow rate and the duration of incline lasted longer especially in cows with a peak flow rate of >3·2 kg/min in routine milking. In milking with a minimum of teat preparation the duration of incline lasted longer compared with the two other treatments. Bimodality of milk flow, i.e. delayed milk ejection at the start of milking, was most frequent at milking with a minimum of teat preparation. No significant differences between routine milking and milking with milk flow-controlled b-phase were detected for all other milking characteristics. In summary, milking with milk flow-controlled b-phase changes the course of milk removal, however mainly in cows with high peak flow rates.

This study was designed to assess the possible effects of mycoplasmas on the quality of milk produced by goat herds in a contagious agalactia (CA) endemic area with absence of classical symptoms. Several factors related to milk quality (percentages of fat, total protein, lactose and total solids, standard plate counts (SPC) and presence of Staphylococcus aureus) were compared in mycoplasma-infected and non-infected herds. To define the CA status of 26 herds on the island of Lanzarote (Spain), where CA is endemic, 570 individual milk samples and 266 bulk tank milk (BTM) samples were microbiologically analysed for the presence of Mycoplasma spp. A herd was considered infected by mycoplasmas when at least a sample (individual or BTM) was positive. BTM samples were also used to determine milk quality parameters. Mycoplasma infection was confirmed in 13 herds. A total of 31, 10 and 11 strains of Mycoplasma mycoides subsp. mycoides LC (MmmLC), Mp. agalactiae and Mp. capricolum subsp. capricolum were isolated. No significant differences were observed between the least square means of the variables fat, total protein, lactose and total solids or SPC recorded for the infected v. non-infected herds. The Staph. aureus status of a herd was also found to be independent of the presence of Mycoplasma spp. Our findings indicate that neither the presence of mycoplasmas in a goat herd with absence of classical symptoms seem to compromise the quality of the BTM.

Unsupplemented acid goat whey containing 0·96% protein and 2·76% lactose was fermented aerobically with 32 microflora extracted from various raw milk cheeses and dairy products. These microflora were screened for their ability to hydrolyse whey proteins (α-lactalbumin and/or β-lactoglobulin) and to generate peptides inhibitors of Angiotensin I Converting Enzyme. Five microflora were able to degrade whey protein. The most efficient microflora was able to fully hydrolyse α-lactalbumin and to a lesser extend β-lactoglobulin. It was extracted from Bamalou des Pyrenées cheese. Micro-organisms involved consisted of yeast Kluyveromyces marxianus and lactobacillus Lactobacillus rhamnosus. Both were able to produce ACE inhibitory peptides after whey fermentation.

Mastitis is the most frequent and costly disease in dairy herds, as it negatively affects yield and milk quality. The presence of clinical mastitis is quite easy to asses, whereas the diagnosis of the subclinical form can be more difficult and requires laboratory assays. Somatic cell count (SCC) is widely used as a rapid and low-cost indicator of mastitis, even if is not useful in discriminating between the clinical and subclinical form. As amyloid A has been investigated as a marker of mastitis, the aim of this study was to assess the potential value of measuring amyloid A in serum and milk and the correlation with SCC in the diagnosis of subclinical mastitis. The reliability of two different ELISA kits for the measurement of amyloid A in milk was also tested. During a 1-month trial period, 21 cows were assigned to three experimental groups according to their health status: 6 cows with clinical mastitis (CM), 10 cows with subclinical mastitis (SM) and 5 healthy cows (HE). Amyloid A was measured both in serum (SAA) and in quarter milk samples (mAA) with a serum ELISA kit, and in quarter milk samples (MAA) with a milk ELISA kit. SCC, total microbial count (TMC) and bacterial examination of the milk were also carried out. After a log transformation, the data were submitted to ANOVA and linear regression. TMC was significantly higher in cows with clinical mastitis, while no differences were observed between the other two experimental groups. SCC and MAA levels were significantly different among the three groups. mAA concentrations were similar between cows with subclinical and clinical mastitis, and SAA was not affected by mastitis. A significant correlation between SCC and MAA or mAA was detected, while no correlation was recorded between SAA and mAA. A close relationship between MAA and mAA was noticeable even at low concentrations, suggesting MAA as a potential physiological marker of subclinical mastitis.

CLA levels and fatty acid composition were measured to compare the fat composition in organic bulk milk, destined to the production of Grana Padano cheese, with those produced by conventional system. The curds and Grana Padano cheeses were also analysed to evaluate the effects of the production technology on the CLA content. All analysed organic samples were characterized by higher annual means of CLA, vaccenic acid (TVA) and linolenic acid (LNA) in comparison with conventional samples (with P<0·05). Nevertheless, no particular effect of the production technology was seen on the CLA content. The animal diet appears to be the factor which has the highest effect on the CLA concentration in milk and milk products and an organic diet based on fresh or dried forage, that is rich in CLA precursory fatty acids, may improve the yield of fatty acids with beneficial effects on health.

Sow milk protects the piglet against infectious diseases through a variety of mechanisms. In this study, the presence of potentially probiotic lactic acid bacteria in this biological fluid was investigated. Milk samples were obtained from 8 sows and a total of 19 rod-shaped isolates were selected for identification and assessment of their probiotic potential. RAPD profiling revealed the existence of 8 different genetic profiles among them. One representative of each profile was selected for further characterization and they were identified as Lactobacillus reuteri, Lb. salivarius, Lb. plantarum, Lb. paraplantarum, Lb. brevis and Weissella paramesenteroides. Then, their probiotic potential was evaluated through different assays, including survival in conditions simulating those existing in the gastrointestinal tract, production of antimicrobial compounds, adherence to intestinal mucin, production of biogenic amines, degradation of mucin, and pattern of antibiotic sensitivity. Three strains, Lb. reuteri CR20 (a reuterin-producing strain), Lb. salivarius CELA2 (a bacteriocin-producing strain) and Lb. paraplantarum CLB7 displayed the highest probiotic potential.

The aim of the present work was to perform a physico-chemical, descriptive quantitative and consumer-preference analysis of hard ewes'-milk cheeses that had been matured for one year and to determine the correlations between the variables studied. The cheeses were elaborated with milk from three breeds of sheep (Castellana, Churra and Assaf) with different somatic cell counts (lower than 500 000 cells ml−1; between 1 000 000 and 1 500 000 cells ml−1, and more than 2 500 000 cells ml−1). The results show that the cheeses elaborated with milk with high SCC had lower values of dry extract and fat and high values of pH and fat acidity and were described as pungent, granulose and less creamy. Regarding the effect of breed, the cheeses made with milk from the Churra breed had lower values for fat and those made with Assaf breed milk were significantly more rancid. The study of correlations showed that creaminess was positively correlated with the dry extract and total fat content and negatively correlated with ash and fat acidity, indeed grainy texture and pungency had the opposite sign in their correlation with these latter variables. The yellow colour was positively correlated with ash and negatively with protein. Finally, the consumer preferences reveals that the less accepted cheeses showed the higher values for rancidness and pungency and they were less likely to accept the cheeses made with Assaf breed milk.

We investigated the anti-allergic effects of one strain (T120) of a lactic acid bacteria (LAB) isolated from Mongolian fermented milk using atopic dermatitis (AD) model mice (NC/Nga mice). Strain T120 has already been identified as Enterococcus faecium and shown to induce strong production of IL-12 (Kimura et al. 2006). In in vitro studies, strain T120 suppressed total IgE production and induced IL-12 and IFN-γ production by splenocytes of NC/Nga mice. The additional examination of various neutralization antibodies was performed to elucidate in detail the mechanism of depressed IgE production by strain T120. As a result, it became clear that IL-12 induced by strain T120 increased production of IFN-γ and total IgE production was mainly controlled by the IFN-γ. In order to define the cells which produce IL-12 powerfully by this strain, antigen-presenting cells (APCs) such as macrophages and dendritic cells (DCs) were removed from the splenocytes, and the reactivity of these cells to the strain was examined. Induction of IL-12 and IFN-γ by strain T120 became significantly very low by removal of APCs from splenocytes. Therefore, it was clear that strain T120 acted on APCs and induced production of IL-12. Further, this strain enhanced the production of IL-10 by splenocytes. In in vivo studies, intraperitoneal injection of strain T120 inhibited serum IgE elevation and atopic dermatitis symptoms in NC/Nga mice. These results suggest that an anti-allergic effect of strain T120 depends on the increased production of IL-12 by APCs activated by the strain and following the increased production of IFN-γ. Further, activation of regulatory T cells by strain T120 may inhibit atopic desease.

Cows with isolation of Staphylococcus aureus approximately 1 week after calving and milk yield, somatic cell count (SCC), clinical mastitis (CM), and culling risk through the remaining lactation were assessed in 178 Norwegian dairy herds. Mixed models with repeated measures were used to compare milk yield and SCC, and survival analyses were used to estimate the hazard ratio for CM and culling. On average, cows with an isolate of Staph. aureus had a significantly higher SCC than culture-negative cows. If no post-milking teat disinfection (PMTD) was used, the mean values of SCC were 42 000, 61 000, 68 000 and 77 000 cells/ml for cows with no Staph. aureus isolate, with Staph. aureus isolated in 1 quarter, in 2 quarters and more than 2 quarters respectively. If iodine PMTD was used, SCC means were 36 000; 63 000; 70 000 and 122 000, respectively. Primiparous cows testing positive for Staph. aureus had the same milk yield curve as culture-negative cows, except for those with Staph. aureus isolated in more than 2 quarters. They produced 229 kg less during a 305-d lactation. Multiparous cows with isolation of Staph. aureus in at least 1 quarter produced 94–161 kg less milk in 2nd and >3rd parity, respectively, and those with isolation in more than 2 quarters produced 303–390 kg less than multiparous culture-negative animals during a 305-d lactation. Compared with culture-negative cows, the hazard ratio for CM and culling in cows with isolation of Staph. aureus in at least 1 quarter was 2·0 (1·6–2·4) and 1·7 (1·5–1·9), respectively. There was a decrease in the SCC and in the CM risk in culture-negative cows where iodine PMTD had been used, indicating that iodine PMTD has a preventive effect on already healthy cows. For cows testing positive for Staph. aureus in more than 2 quarters at calving, iodine PMTD had a negative effect on the CM risk and on the SCC through the remaining lactation.